you level up in battles, for every action - succesfull hits ,abilities and spells, in FFTA you had the option to show how much XP you got, now you don't and the characters don't level in battle like before but only after battle, which sucks
Edit: sry you probably mean the gauge with the job written in it, I think you fill it with every ability you learn for this job
ps: anybody knows what is the smash gauge for? it's the one that on the side of the character picture and stats(hp, mp) in
and also what the MVP stands for? most valuable player? how is it awarded? and what is the totem-like gauge with MVP under it for?
played for nearly 30 hours and I still don't get many parts of the game and if I hadn't completed FFTA (all 300 missions, over 50 hours

) I would be pretty lost even in the jobs and their acquiring, this game really has a veeeeery steep learning curve